Cardiolipin Antigens in the Kolmer Complement Fixation Test for Syphilis
This archive record revisits A. Harris and J. Portnoy’s 1944 study of cardiolipin, lecithin, and cholesterol mixtures for the Kolmer complement-fixation test, focusing on reproducibility, sensitivity, specificity, storage stability, and the study’s place in the later development of lipoidal-antigen syphilis serology.
What the study did and found
The original publication, “Cardiolipin Antigens in the Kolmer Complement Fixation Test for Syphilis,” by A. Harris and J. Portnoy was published in 1944 in Venereal Disease Information. The study examined whether defined mixtures of cardiolipin, lecithin, and cholesterol could reduce the variability seen with beef-heart antigens used in the Kolmer complement-fixation test. Twenty-three formulations were prepared and tested. The study reported acceptable sensitivity with cardiolipin at 0.03–0.06%, cholesterol at 0.3–0.6%, and lecithin at 0.05%. Antigen 21 produced results almost identical to a standard Kolmer antigen in 370 test sera. The preparations were also reported to remain stable for at least one year when stored in the dark at room temperature.
Why it is cited
The paper is cited in the historical literature because it documented an early effort to standardize syphilis serology by replacing less consistent tissue-derived antigen preparations with defined lipid mixtures. Later work on cardiolipin antigens and complement-fixation methods referred to Harris and Portnoy as part of the methodological development of serologic testing.
Modern syphilis testing no longer uses the Kolmer complement-fixation test as a central diagnostic method. However, the cardiolipin-based principle remains relevant. Current CDC laboratory guidance describes RPR and VDRL as nontreponemal tests using lipoidal antigen mixtures containing cardiolipin, cholesterol, and phosphatidylcholine. These tests are not specific for Treponema pallidum and are interpreted together with treponemal tests. The 1944 findings are therefore historically important for reagent standardization, but they should not be treated as direct validation of current commercial assays or present-day diagnostic algorithms.
For current laboratory terminology and recommendations, see the CDC Laboratory Recommendations for Syphilis Testing, United States, 2024.
The topic today
Today, cardiolipin-based reactions remain part of syphilis serology through RPR and VDRL testing. These nontreponemal tests can support screening, diagnosis, and treatment monitoring through quantitative titers, while treponemal tests provide greater specificity. The historical Harris-Portnoy study illustrates an important stage in the shift toward more reproducible serologic reagents, whereas current clinical interpretation depends on validated modern testing algorithms and laboratory guidance.